While he’s correct Android is the dominant operating system, he’s
incorrect that it’s the platform developers should be working on
primarily. Proof of that comes from today’s Instagram acquisition.
Facebook paid $1 billion for a company that was iOS exclusive
until last week.

I’d say Instagram’s success and high acquisition price show that iOS is the dominant mobile platform. Market share is a factor in dominance, but clearly not the only one.

Maybe Instagram would have been better served by shipping an Android port sooner. Maybe they should have had a web-based interface. But the fact remains that they built a photo sharing social network with 30 million users and over one billion photos with just one client: an iPhone app.